<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
</head>
<body>

<script type="text/javascript">

var a = 10;
delete a;
alert(a);

c = 10;
delete c;
alert(c)

function b(){
   this.c = 10;
};

delete new b().c

</script>
</body>
</html>